Apparatus and method for enlarging holes

ABSTRACT

A tool for enlarging the diameter of holes through work pieces including a mandrel with an expansion section thereon of a diameter larger than the initial diameter of the holes, driving means for forcing the mandrel through the holes to enlarge same, and a backup member with an aperture therethrough of a diameter at least as small as the initial diameter of the holes that is positioned against the work pieces in opposition to the mandrel with its aperture aligned with the holes. The aperture of the backup member is enlarged simultaneously with the enlargement of the holes immediately adjacent the backup member so as to support the material of the work pieces about the holes at all times during the enlargement of the holes. The method of using the tool is also disclosed.

ilnited States Patent [1 1 King, Jr.

[ APPARATUS AND METHOD FOR ENLARGING HOLES [76] Inventor: John 0. King, Jr., 3990 N. Ivy Rd., Atlanta, Ga. 30342 122] Filed: Jan. 17, 1973 [211 Appl. No.: 324,484

[52] US." Cl 72/370, 29/446, 72/391 [51] Int. Cl B21k 21/16 [58] Field of Search 72/370, 391; 29/446, 523

[56] References Cited UNITED STATES PATENTS 2,185,483 1/1940 Ward 29/523 3,270,410 9/1966 Salter et al... 3,434,327 3/1969 Speakman.... 3,445,908 5/1969 Straub 3,566,662 3/1971 Champoux 72/370 Apr. 23, 1974 Primary Examiner-Lowell A. Larson 9 57 ABSTRACT A tool for enlarging the diameter of holes through work pieces including a mandrel with an expansion section thereon of a diameter larger than the initial diameter of the holes, driving means for forcing the mandrel through the holes to enlarge same, and a backup member with an aperture therethrough of a diameter at least as small as the initial diameter of the holes that is positioned against the work pieces in opposition to the mandrel with its aperture aligned with the holes. The aperture of the backup member is enlarged simultaneously with the enlargement of the holes immediately adjacent the backup member so as to support the material of the work pieces about the holes at all times during the enlargement of the holes. The method of using the tool is also disclosed.

10 Claims, 9 Drawing Figures FATENTEBAPHB I974 3.805578 SHEET 2 UF 2 HOL E5 RKPIECES BACKGROUND OF THE INVENTION Techniques and expansion tools for enlarging the effective diameter of holes through work pieces are available on the market today. Such prior art systems usually included a mandrel with an expansion section thereon of a diameter larger than the initial diameter of the holes through the work pieces and which was pulled or forced through the holes of the work pieces to enlarge the effective diameter of the holes. One of the problems with these prior art systems is that when the holes were enlarged an appreciable amount, the excessive forces generated within the material about the holes caused the material at that end of the holes from which the mandrel exited to be extruded outwardly to form an undesirable lip about that end of the holes. This was because the material about the holes was not adequately supported. The lip has caused improper seating of the fasteners that are usually installed in the hole after they are enlarged to produce an unsatisfactory joint.

SUMMARY OF THE INVENTION The invention disclosedherein overcomes these and other problems associated with the prior art hole enlarging systems in that means is provided whereby the extruded lip around that end of the-hole from which the enlarging mandrel was withdrawn is not formed. The apparatus of the invention includes generally a mandrel with an expansion section of a diameter a certain amount larger than the initial diameter of the holes through the work pieces to be enlarged with a smaller diameter support section which can be received through the holes prior to enlargement and which can be engaged by a lockbolt installation tool to withdraw the expansion section of the mandrel through the holes. A backup member having an aperture therethrough at least'as small as the holes through thework pieces prior to enlargement is positioned onto the smaller diameter support section of the mandrel so that the backup member will be on the opposite. side of the work pieces from the expansion section of the mandrel. The backup member is sufficiently strong in compression to prevent its collapse during the withdrawing of the expansion section through the holes but is sufficiently weak in radial expansion to allow the aperture to be enlarged along with the material of the workpieces immediately adjacent the backup member as the expansion section of the mandrel passes therethrough. Thus, the material around the holes through the work pieces that were normally extruded in the prior art is precluded from doing so by the backup member.

The method of the invention includes the holding of the backup member set forth above on that side of the work pieces opposite that from which the expansion section of the mandrel enters thework'pieces to prevent a lip from being extruded about that end of the hole from which the'expansion section exits.

These and other features and advantages of the invention will become more fully understood upon consideration of the following specification and accompanying drawings wherein like characters of reference designate corresponding parts throughout the several views and in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of one embodiment of the invention;

FIG. 2 is an enlarged cross-sectionalview of one embodiment of the backup member; I

FIG. 3 is an enlarged cross-sectional view of another embodiment of the backup member;

'FIG. 4 is a view showing the tool of the invention in position for enlarging holes through work pieces;

FIG. 5 is a view similar to FIG. 4 showing the mandrel passing out of the holes through the work pieces;

FIG. 6 is an enlarged portion of FIG. 5;

FIG. 7 is a cross-sectional-view of holes enlarged by the prior art; o

FIG. 8 is a cross-sectional view of holes enlargedby the invention; and, i

FIG. 9 is a viewsimilar to FIG. 4 for countersunk holes. These figures and the following detailed description disclose specific embodiments of the inventiom'however; the inventive concept is not limited thereto since it maybe embodied in other forms.-

. DETAILED DESCRIPTION or ILIL usTRATIvE' v EMBODIMENTS I Referring to the figures, the apparatus of the invention comprises mod 10 for use with a driving unit 11. The tool 10 as seen in FIGS. 1-6 includes a mandrel l2 and a backup member 14 positionable on the mandrel 12. The mandrel 12 is withdrawn through holes H in work pieces P to enlarge the holesto a final'size. The holes II have an initial diameter D, seen in FIG. 4 prior to enlargement and an enlarged diameter D seen .in

FIG. 8 after the mandrel l2has been forced therethrough.

As seen in FIGS. 1-6, themandrel l2has an expansion-section 15 at one, end, a central support section 16,

anda gripping section 18 at the opposite end thereof. The expansion section 15 defines a cylindrical sizing surface 19 at its free end with a tapered expansion surface 20 connecting. the surface 19 with the support sec.- tion -16. The diameter d of the sizing surface l9'is larger'than the initial diameter D, of the holes H and the diameter d of the support section 16 is smaller than theinitial diameter D, of the holes H. The gripping section 18 is adapted to be gripped by the unit 11 as will be explained.

The driving unit 11 includes an'adapter 21 and a commercially available lockbolt installation tool (not shown) with a self-releasing pulling nose assembly N (partly shown). The gripping section 18 is provided with grooves and ridges to be engaged by the nose assembly N. The adapter 21 has a large diameter recess 22 receivable over the end of the nose assembly N with a passage 24 through the end thereof aligned with thehole in the end of nose assembly N when the adapter is in position as shown in FIG. 4. The passage 24' has a diameter such that the sizing surface 19 will just slidably pass therethrough. The adapter 21 serves as a spacer to prevent the expansion section 15' of mandrel 12 from being caught in the nose assemblyN since this section is normally larger in diameter than the opening in the end of the nose assembly. The adapter 21 is also removable from the nose assembly N so that the mandrel 12 can be easily removed from the nose assembly manually.

The backup member 14 is best seen inFIGS. 2 and 3. The member 14a in FIG. 2 is for use ,when enlarging plain holes H and the member 14b in FIG. 3 is for use when enlarging countersunk holes H. Member 14a is washer shaped and defines a central aperture 30 therethrough with a diameter d at least as small as the initial diameter D, of the holes H but larger than the diameter d so that the member 14a can be slipped onto the support section 16 of the mandrel. Member 14a has working faces 31', each of which is adapted to face the near side of the work pieces. Faces 31 are normal to the aperture 30 and parallel. A protruding lip 32 is provided about the aperture 30 on each face 31. This lip 32 has an outer surface 34 with a concave cross-section of a radius r that'conforms tothefilet radius between the head and shank of a fastener that .willbe used in' the holes.

The backup member 14a has a thickness t and an outside diameter d., such that the member is sufficiently strong incompression through its thickness to not collapse as themandrel 12'is being withdrawn to enlarge the holes H, but sufficiently weak in a, radial direction to allow the expansion section to expand same and enlarge the aperture 30 so that section 15 can pass therethrough as seen in FIG. 5. Because the tapered expansion surface 19 of the section 15 expands the aperture 30 at the same ratethe holes H adjacent the aperture 30 are being expanded, that section of the material of the work pieceslying adjacent the holes H is supported to prevent the formationof the extruded lip that was present in the prior art. This is best seen in FIG. 6. Thus, asmooth edge is provided about the holes H after they have been expanded to their final size as seen in FIG. 8. i The member 14b shown in FIG. 3 is also generally washer shaped with a central aperture 30 like aperture 30 in member 140. Aperture 30' has a diameter d like that of aperture 30 so that the member 14b can be slipped onto the support section 16 of the mandrel 12. Unlike the member 14a, member 14b has a working face 31' which is tapered to conform tothat of a coun-. tersink in countersunk holes H. Member 14b has an opposit'e face 33 which is'normal to aperture 30' like face 31 of member 14a; Because the-intersection of the tapered face 31 with the aperture. 30 forms a lip 32', there is no need for theadditional lip required as with the member 14a. The member 14!: has a maximum thickness t and an outside diameter (1., such that the member will not collapse as the mandrel is being withdrawn to enlarge holes H but will allow the aperture 30 to be expanded as the expansion section 15 passes therethrough simultaneously enlarging the holes H immediately adjacent the member 14b.

The diameter d, of the sizing surface 19 is usually larger than the initial diameter D, of the holes H in the range of 0.0050.030 inch, depending on the desired amount the holes H are to be enlarged to the diameter D The diameter (1 of the support section'16 is usually smaller than the initial diameter D, of the holes H in the range of 0.00 l- 0.0lO inch so that the section 16 can be easilyinserted into the holes H. The diameter d of the aperture 30 through backup member 14 is usually equal to or slightly smaller than the initial diameter D, in the order of 0.00l inchtoinsure that the material of the work pieces P immediately adjacent the holes H and the member 14 will be adequately supported during the enlargement of the holes H to prevent extrusion of the lip around the holes as was present in the prior art. The thicknesses t and 1 may be varied as long as the above criteria is met, however, it has been found that a thickness in the order of 0.125 inch is sufficient for both members 14a and 14b. The diameters d, and 11., may also be varied, however, it has been found that a diameter d, in the order of 0.1250.250 inch larger than diameter d is sufficient and a diameter d., in the order of 0.250-0.500 inch larger than diameter d,. While various materials may be used for members 14, it has been found that a mild annealed steel performs satisfactorily using the. dimensions set forth above. Of course,'it is to be understood that differentdiameters d ,d ,d and d will be used for different diameters D, of the holes H.

OPERATION .is forced throughthe holes H. The diameter d is smaller than diameter D, and the support section 16 is inserted through the. holes H from the off side of work pieces P until the expansion section 15 is adjacent the holes H as seen in FIG. 4. Then the backup member 14a or 14b, depending on whether holes H are plain or countersunk, is inserted over the gripping section 18 and onto the support section 16 so that its working face 31or 31" lies in juxtaposition with the near side work piecesP about the holes H. I

The adapter 21 is slipped onto the nose assembly N and the mandrel 12 is held in position while the section 18 passes through the passage 24 into engagementwith the pulling jaws (not shown.) of the nose assembly N. The installation. tool (not shown) is then actuated in known manner to cause the nose assembly N to force the member 14 and expansion section 15 of mandrel 12 toward. each other. This causes the work pieces to. be clamped between the member 14 and the section 15, and forces the expansion section 15 through the holes H from the far side toward the near side. This expands theholes H as seen in FIGS. 5, 6 and 8. As the tapered surface 20 passes out of holes H,.itengages the member 14 as best seen in FIG. 6 to expand the aperture 30 therethrough simultaneously with the expansion of the holes H immediately adjacent the member 14. Thus, that edge of the holes H on the near side of the work pieces P is supported at all times during the passage of the expansion section 15 through holes H to prevent extrusion of the lip about the holes H as was encountered in the prior art. A lip L may be extruded on the member 14 as seen in FIG. 8 about the aperture 30 on that side of member 14 from which the section 15 exits. The lip L, however, has no detrimental effect on the work pieces P since the member 14 is discarded after the expansion of aperture 30. The member 14 cannot be reused in subsequent hole enlarging operations since the enlarged aperture 30 would not adequately support the work pieces to prevent alip from being extruded about the holes of the work pieces. 7 j I When countersunk holes H with a countersink C are to be enlarged, the tapered working face 31 of backup member 14b fits into the countersink C to support same. As the mandrel 12 is withdrawn through the holes H, a sufficient force is exerted on countersink C through member 14b to work the countersink C. Previously, the countersink C had to be formed after the mandrel had passed through the holes.

It has been found that a small amount of the work pieces may stick to the mandrel 12 as it is pulled through the holes. While only a minute amount of material of the work pieces may stick to the mandrel each time it passes through the holes, it has been found that such amounts are cumulative so that as the amount of material of the work pieces builds up on the mandrel, galling of the holes takes place. To prevent this from occurring, the material is cleaned from the mandrel after each passage through the holes. This can be accomplished by chucking the mandrel in an appropriate rotational device and holding a fine grade of sandpaper or polishing cloth against the mandrel to remove the material. Because the mandrel is made of a very high quality tool steel and is therefore very hard, this cleaning operation does not effect the dimensions of the mandrel.

Because of the high friction forces which may be encountered between the mandrel, it is usually neceasary to lubricate the mandrel. While various lubricants may be used, a dry film lubricant which is commercially available may be used to coat the mandrel prior to each use, especially if the amount of enlargement of the holes is to be substantial.

l claim l. A tool for enlarging holes through work pieces including:

a mandrel having an expansion section of a diameter a prescribed amount larger than said holes prior to enlargement;

a backup member having an aperture therethrough at least as small as said holes prior to enlargement; and

drive means for forcing said expansion section through said holes to enlarge the diameter thereof while holding said backup member against said work pieces in opposition to said expansion section of said mandrel and substantially concentric with said holes, said backup member being made out of a material thatallows said expansion section of said mandrel to be forced therethrough to enlarge said aperture therethrough simultaneously with the enlargement of that portion of said holes immediately adjacent said backup member.

2. The tool of claim 1 wherein said backup member is washer shaped and defines a supporting surface for supporting the work pieces immediately adjacent the edges of the holes to prevent the materialof the work pieces from being extruded as said mandrel is forced therethrough.

3. The tool of claim 2 wherein said supporting surface is normal to said aperture and wherein said backup member further includes a supporting lip protruding from said supporting surface about said aperture and facing said work pieces, said lip having a concave outside surface.

4. The tool of claim 2 for use in enlarging countersunk holes wherein said supporting surface is tapered to fit within the countersink at said holes.

5. The tool of claim 1 wherein said aperture has a diameter a prescribed amount smaller than the initial diameter of the holes.

6. The tool of claim 1 wherein said mandrel further includes a support section of a diameter smaller than said holes connected to said expansion section so as to extend through said holes prior to enlargement thereof and to slidably support said backup member thereon during enlargement of said holes.

7. A tool for use with a lockbolt installation tool to enlarge holes through work pieces including:

an elongate mandrel comprising an expansion section at one end thereof; a central support section integral with said expansion section at one of its ends, and a gripping section integral with said support section opposite said expansion section; said sup-. port section having a diameter smaller than the initial diameter of the holes so as to be slidably received therethrough, said expansion section includ ing a cylindrical portion of a diameter larger than the initial diameter of the holes and a tapered portion connecting said cylindrical portion with said support section; and said gripping section adapted to be engaged by the lockbolt installation to pull said expansion section through the holes to enlarge same;

a backup member having a washer shape and defining an aperture therethrough of a diameter larger than the diameter of said support section and smaller than the initial diameter of the holes slidably receivable over said support section; 1 said backup member defining a working face adapted to engage and support one side of said work pieces immediately adjacent the holes and an opposite face normal to said aperture, said backup member being made of a material that is sufficiently strong in compression to prevent the collapse thereof but sufficiently weak in radial tension to allow said expansion section to be forced through said aperture to enlarge same; and,

an adapter constructed and arranged to be removably mounted on the operating end of the lockbolt installation tool and defining a central passage .therethrough of a diameter sufficiently large to slidably receive said cylindrical portion of said mandrel therethrough, so that when said support section is inserted through the holes and said backup member placed on said support section with said working face facing said work pieces in opposition to said expansion section, said lockbolt installation tool can engage said gripping section after passage through said adapter to pull said expansion section through the holes while forcing said backup member toward the work pieces to enlarge the holes and said aperture through said backup member.

8. Apparatus for enlarging holes in work pieces comprising in combination:

I a mandrel having an outside larger and an outside smaller diameter, said larger diameter larger than the diameter of the holes prior to enlargement and said smaller diameter smaller than the, diameter of the holes prior to enlargement; and,

a backup member having an aperture therethrough at least as small as the diameter of the holes and larger than said smaller diameter of said mandrel so that when said smaller diameter is inserted through the holes and said backup member positioned on said smaller diameter in opposition with said larger diameter across said work pieces, said larger diameter and said backup member can be forced toward each other to cause said larger diameter to pass through the holes and said aperture to enlarge the diameter thereof.

9. A method of enlarging holes through work pieces including the steps of:

a. forcing a mandrel having an expansion section of a diameter larger than the initial diameter of the holes through the holes to enlarge their diameter; and,

b. supporting the material of the work pieces about the holes from that side of the work pieces toward which said mandrel is moving with a back-up member having an aperture therethrough at least as small as the initial diameter of the holes which is aligned with the holes and through which the expansion section passes to enlarge the aperture simultaneously with the enlargement of the holes immediately adjacent the back-up member.

10. A method of enlarging holes through work pieces comprising the steps of:

positioning an expansion mandrel and a backup member with an aperture therethrough on opposite sides of the work pieces in alignment with the holes of the work pieces; and,

forcing the mandrel and backup member toward each other to cause the mandrel to pass through the holes in the work pieces and the aperture in the backup member to enlarge same. 

1. A tool for enlarging holes through work pieces including: a mandrel having an expansion section of a diameter a prescribed amount larger than said holes prior to enlargement; a backup member having an aperture therethrough at least as small as said holes prior to enlargement; and drive means for forcing said expansion section through said holes to enlarge the diameter thereof while holding said backup member against said work pieces in opposition to said expansion section of said mandrel and substantially concentric with said holes, said backup member being made out of a material that allows said expansion section of said mandrel to be forced therethrough to enlarge said aperture therethrough simultaneously with the enlargement of that portion of said holes immediately adjacent said backup member.
 2. The tool of claim 1 wherein said backup member is washer shaped and defines a supporting surface for supporting the work pieces immediately adjacent the edges of the holes to prevent the material of the work pieces from being extruded as said mandrel is forced therethrough.
 3. The tool of claim 2 wherein said supporting surface is normal to said aperture and wherein said backup member further includes a supporting lip protruding from said supporting surface about said aperture and facing said work pieces, said lip having a concave outside surface.
 4. The tool of claim 2 for use in enlarging countersunk holes wherein said supporting surface is tapered to fit within the countersink at said holes.
 5. The tool of claim 1 wherein said aperture has a diameter a prescribed amount smaller than the initial diameter of the holes.
 6. The tool of claim 1 wherein said mandrel further includes a support section of a diameter smaller than said holes connected to said expansion section so as to extend through said holes prior to enlargement thereof and to slidably support said backup member thereon during enlargement of said holes.
 7. A tool for use with a lockbolt installation tool to enlarge holes through work pieces including: an elongate mandrel comprising an expansion section at one end thereof; a central support section integral with said expansion section at one of its ends, and a gripping section integral with said support section opposite said expansion section; said support section having a diameter smaller than the initial diameter of the holes so as to be slidably received therethrough, said expansion section including a cylindrical portion of a diameter larger than the initial diameter of the holes and a tapered portion connecting said cylindrical portion with said support section; and said gripping section adapted to be engaged by the lockbolt installation to pull said expansion section through the holes to enlarge same; a backup member having a washer shape and defining an aperture therethrough of a diameter larger than the diameter of said support section and smaller than the initial diameter of the holes slidably receivable over said support section; said backup member defining a working face adapted to engage and support one side of said work pieces immediately adjacent the holes and an opposite face normal to said aperture, said backup member being made of a material that is sufficiently strong in compression to prevent the collapse thereof but sufficieNtly weak in radial tension to allow said expansion section to be forced through said aperture to enlarge same; and, an adapter constructed and arranged to be removably mounted on the operating end of the lockbolt installation tool and defining a central passage therethrough of a diameter sufficiently large to slidably receive said cylindrical portion of said mandrel therethrough, so that when said support section is inserted through the holes and said backup member placed on said support section with said working face facing said work pieces in opposition to said expansion section, said lockbolt installation tool can engage said gripping section after passage through said adapter to pull said expansion section through the holes while forcing said backup member toward the work pieces to enlarge the holes and said aperture through said backup member.
 8. Apparatus for enlarging holes in work pieces comprising in combination: a mandrel having an outside larger and an outside smaller diameter, said larger diameter larger than the diameter of the holes prior to enlargement and said smaller diameter smaller than the diameter of the holes prior to enlargement; and, a backup member having an aperture therethrough at least as small as the diameter of the holes and larger than said smaller diameter of said mandrel so that when said smaller diameter is inserted through the holes and said backup member positioned on said smaller diameter in opposition with said larger diameter across said work pieces, said larger diameter and said backup member can be forced toward each other to cause said larger diameter to pass through the holes and said aperture to enlarge the diameter thereof.
 9. A method of enlarging holes through work pieces including the steps of: a. forcing a mandrel having an expansion section of a diameter larger than the initial diameter of the holes through the holes to enlarge their diameter; and, b. supporting the material of the work pieces about the holes from that side of the work pieces toward which said mandrel is moving with a back-up member having an aperture therethrough at least as small as the initial diameter of the holes which is aligned with the holes and through which the expansion section passes to enlarge the aperture simultaneously with the enlargement of the holes immediately adjacent the back-up member.
 10. A method of enlarging holes through work pieces comprising the steps of: positioning an expansion mandrel and a backup member with an aperture therethrough on opposite sides of the work pieces in alignment with the holes of the work pieces; and, forcing the mandrel and backup member toward each other to cause the mandrel to pass through the holes in the work pieces and the aperture in the backup member to enlarge same. 